This project is concerned with the source and function of several species of low molecular weight nuclear (LMN) RNA which are distinct from ribosomal, transfer on messenger RNA. The present focus of the work is on the source of LMN RNAs and experiments are being conducted to answer the following questions: 1) Which class(es) of nuclear RNA polymerase are responsible for the synthesis of LMN RNAs? 2) Which chromosomes or chromosome region in the human complement contain DNA which is complimentary to LMN RNAs? 3) From which complexity class(es) of DNA are LMN RNAs transcribed? 4) Is LMN RNA-DNA clustered or dispersed in the genome?